A belted constant velocity transmission (CVT) is a relatively simple, inexpensive, effective and reliable system for transferring power in vehicles. Belted CVT's are presently used in or have application in vehicles including snowmobiles, all-terrain vehicles, small road racing vehicles and the like. Belted CVTs, albeit more complex versions, also have application in automobiles.
Belted CVT's as used in recreational vehicles such as snowmobiles are relatively efficient in power transfer when properly tuned (i.e., calibrated) for a particular type of usage. In the case of a snowmobile, examples of particular types of usage include mountain trails, touring activities, circle track racing, endurance racing, etc. Overall CVT clutch efficiency in conventional belted CVT's is based on clutch system factors such as, but not limited to, sheave diameter, sheave weight, sheave face angles, belt contact patch area, clutch spring rates, clutch flyweight weights and torque ramp rates. However, clutch spring rates, clutch flyweight weights and torque ramp rates are the factors that are generally tunable by a rider or mechanic once the vehicle leaves the factory.
Conventional belted CVT's and their associated clutch systems exhibit one or more limitations that adversely affect their effectiveness, desirability and/or practicality. One limitation is that clutch system efficiency is application dependent. For example, a clutch tuned for mountain trail riding will generally offer less than desirable efficiency and performance in an endurance racing application. Another limitation is that tunability is limited. Generally speaking, tuning is limited to a few factors (e.g., clutch spring rates, clutch flyweight weights and torque ramp rates) and such factors are only coarsely adjustable (i.e., discrete rates/weights with limited selection). Another limitation is that tuning is time consuming in that it requires the clutch system to be at least partially disassembled and manually tuned. Still another limitation is that achieving effective tuning results is largely based on experience garnished from trial end error.
Therefore, a clutch system for a belted CVT that overcomes limitations associated with conventional clutch systems for belted CVT's would be useful and novel.